1. Field of the Invention
The present invention relates to a liquid ejecting head, a head cartridge, and a liquid ejecting apparatus.
2. Description of the Related Art
Heretofore, there is known an inkjet recording method, that is, a so-called bubble jet recording method by which a state of ink is changed together with a rapid change of its volume (generation of bubbles) by applying energy such as heat and the like thereto, by which the ink is ejected from an ejecting port by operating force based on the change of the state, and by which the ink is deposited on a recording medium so as to form an image thereon. As shown in Japanese Patent Publication Nos. 61-59911 and 61-59914, a recording apparatus using the bubble jet recording method ordinarily includes an ejecting port for ejecting ink, an ink flow path communicating with the ejecting port, a heating element (electro-thermal transducer) as an energy generation means for ejecting ink in the ink flow path.
The above recording method has such many excellent features that an image of high quality can be recorded at high speed with low noise as well as an image recorded by a small apparatus with high resolution and further a color image can be easily obtained because ejecting ports for ejecting ink can be very densely disposed in a head used in the method. Accordingly, the bubble jet recording method is recently utilized in many office equipment such as a printer, copy machine, facsimile and the like and further in an industrial system such as a textile printer and the like.
On the other hand, in the conventional bubble jet recording method, ink may be burned and deposited on the surface of a heating element because it generates heat repeatedly while in contact the ink. Further, when a liquid to be ejected is liable to be deteriorated by heat or when a bubble cannot be sufficiently obtained therefrom, the liquid may not be excellently ejected when it is directly heated by the above-mentioned heating element to form a bubble.
In contrast, the applicant proposes, in Japanese Patent Laid-Open No. 55-81172, a method of ejecting a liquid by forming a bubble from a bubble forming liquid by thermal energy through a flexible membrane which separates the bubble forming liquid from the liquid to be ejected. The flexible membrane and the bubble forming liquid in the method is arranged such that the flexible membrane is disposed at a portion of nozzles. In contrast to the above arrangement, an arrangement in which a large membrane for separating an overall head vertically is disclosed in Japanese Patent Laid-Open No. 59-26270. The large membrane is held by two sheet members for forming two liquid paths for the purpose of preventing liquids in the two liquid paths from being mixed with each other.
On the other hand, Japanese Patent Laid-Open No. 5-229122 discloses an arrangement using a bubble forming liquid having a boiling point lower than that of a liquid to be ejected and Japanese Patent Laid-Open No. 4-329148 discloses an arrangement using a conductive liquid as a bubble forming liquid as arrangements in which bubble forming liquids having features are used and bubble forming characteristics are taken into consideration.
In the heads as described above for completely separating the liquid to be ejected from the bubble forming liquid, it is an important problem to stabilize the state of the bubble forming liquid at all times to perform injection stably.
However, there is a possibility that fine bubbles remain in the bubble forming liquid after bubbles are formed depending upon driving conditions because the bubble forming liquid is not ejected and that the fine bubbles obstruct stable formation of bubbles.
To remove the remaining bubbles, while there are a method of previously deaerate the bubble forming liquid, and the like, the most effective method is to provide a head with a structure capable of removing remaining bubbles.
Thus, the inventors have devised a liquid ejecting head having a structure for ciculating a bubble forming liquid to remove remaining bubbles.
However, in the above head, it is necessary to provide a collection path for circulating the bubble forming liquid, which not only makes the structure of the head complex but also it is necessary to draw or pressurize the bubble forming liquid to circulate it. Accordingly, there is problem that a load applied to the liquid ejecting head and apparatus is increased.
An object of the present invention is to provide a liquid ejecting head, a head cartridge, and a liquid ejecting apparatus capable of removing remaining bubbles in a bubble forming liquid by a simple arrangement as well as of improving an ejecting efficiency by effectively transmitting the pressure of a bubble to a liquid to be ejected.
To achieve the above object, in a liquid ejecting head of the present invention having a first liquid flow path communicating with an ejecting port for ejecting a liquid to be ejected and an element substrate having a heating element for forming a bubble from a bubble forming liquid as well as including a second liquid flow path corresponding to the first liquid flow path and a movable separation membrane for substantially separating the first liquid flow path and the second liquid flow path corresponding to the first liquid flow path from each other at all times, the liquid ejecting head includes an atmosphere communication port facing the atmosphere for communicating the second liquid flow path with the atmosphere, and an atmosphere communication path having an atmosphere communication path introduction port facing the second liquid flow path, wherein the atmosphere communication port is formed through the same surface as that of the ejecting port.
The liquid ejecting head arranged as described above includes the atmosphere communication path for communicating the second liquid flow path, in which the bubble forming liquid exists, with the atmosphere and removes remaining bubbles generated in the second liquid flow path from the atmosphere communication path. That is, the liquid ejecting head is provided only with the communication path for communicating the second liquid flow path with the atmosphere as an arrangement for removing the remaining bubbles, and it is not necessary to provide the liquid ejecting head with a collection path for collecting the remaining bubbles, a mechanism for circulating the bubble forming liquid, and the like. Further, since the atmosphere communication path and the ejecting port are formed through the same surface, when the liquid to be ejected in the ejecting port is drawn by a drawing device having a drawing unit abutted against the ejecting port in order to restore, for example, the ejecting capability of the ejecting port, the remaining bubbles in the atmosphere communication path also can be drawn and removed without changing a direction in, which the drawing unit of the drawing device is abutted simultaneously with the restoration of the ejecting capability.
In a liquid ejecting head of the present invention, when the ejecting port has an area S0 and the atmosphere communication port has an area S1, a relationship of S1xe2x89xa6S0 may be established. When the above relationship is established, in particular, when the atmosphere communication path, the atmosphere communication path introduction port, and the atmosphere communication port have the same sectional area and the area of the atmosphere communication port is smaller than that of the ejecting port as represented by S1 less than S0, it scarcely occurs that the bubble forming liquid is ejected from the atmosphere communication port of the atmosphere communication path by the influence of ejection of the liquid from the ejecting port. Further, when the ejecting port has an area S0, the atmosphere communication port has an area S1 and the atmosphere communication path introduction port has an area S2, relationships of S0 less than S1 and S2 less than S1 may be established. When the above relationships are established, the area of the atmosphere communication path introduction port is smaller than that of the atmosphere communication port. Thus, first, it is difficult for ejection energy to be transmitted up to the atmosphere communication port through the atmosphere communication path introduction port. Further, since the area of the atmosphere communication port is large than that of the ejecting port, a large amount of ejection energy is necessary to eject the bubble forming liquid from the atmosphere communication port, which makes it difficult for the bubble forming liquid to be ejected from the atmosphere communication port. As a result, it is possible to dispose the atmosphere communication path introduction port in the vicinity of a bubble generating region where a bubble is generated in the bubble forming liquid by a heating element, which increases a remaining bubble removing efficiency.
When it is supposed that a supply source of the bubble forming liquid is located upstream, the atmosphere communication path introduction port may be formed downstream of the heating element. In this case, since the atmosphere communication path introduction port is formed downstream, it can be prevented that the bubble forming liquid stagnates downstream of the heating element of the second liquid flow path.
An expanded section, which has an sectional area sufficient to pevent bubble forming liquid from rising up to the atmosphere communication port from the atmosphere communication path introduction port by capillary force, may be formed in the midway of the atmosphere communication path. In this case, since the liquid boundary of the bubble forming liquid cannot pass the expanded section, even if the bubble forming liquid is ejected from the atmosphere communication path introduction port, it is ejected into the expanded section. Thus, the bubble forming liquid is not directly ejected to the outside from the atmosphere communication port. Further, the projecting surface of the atmosphere communication port and the atmosphere communication path introduction port of the atmosphere communication path may not overlap each other. In this case, even if the bubble forming liquid is ejected from the atmosphere communication path introduction port, it is not ejected to the atmosphere communication port but is ejected to a wall surface which forms the expanded section. As a result, direct ejection of the bubble forming liquid to the outside from the atmosphere communication port can be more reliably prevented. Further, a plurality of the atmosphere communication path introduction ports may be formed with respect to one atmosphere communication path or a plurality of the atmosphere communication paths may be formed.
When the plurality of atmosphere communication paths are formed, a desired opening area required to the atmosphere communication path introduction ports of the atmosphere communication paths and the atmosphere communication ports can be shared by the respective atmosphere communication paths. That is, when necessary, the opening areas of the respective atmosphere communication path introduction ports and the respective atmosphere communication ports can be reduced. The movable separation membrane may be an organic film formed by a deposition method by chemical vapor reaction or plasma polymerization reaction. In this case, the movable separation membrane may contain ployparaxylene.
A head cartridge of the present invention includes a liquid ejecting head photographic film the present invention and an ink tank for holding a liquid to be ejected by the liquid ejecting head.
In the head cartridge arranged as described above, the liquid ejecting head includes the atmosphere communication path for communicating the second liquid flow path, in which the bubble forming liquid exists, to the atmosphere and removes remaining bubbles generated in the second liquid flow path from the atmosphere communication path. That is, the liquid ejecting head of the head cartridge is provided only with the communication path for communicating the second liquid flow path with the atmosphere as an arrangement for removing the remaining bubbles, and it is not necessary to provide the liquid ejecting head with a collection path for removing the remaining bubbles, a mechanism for circulating the bubble forming liquid, and the like. Further, in the liquid ejecting head provided with the head cartridge of the present invention, since the atmosphere communication path and the ejecting port are formed through the same surface, when the liquid to be ejected in the ejecting port is drawn by a drawing device having a drawing unit abutted against the ejecting port in order to restore, for example, the ejecting capability of the ejecting port, the remaining bubbles in the atmosphere communication path also can be drawn and removed without changing a direction in which the drawing unit of the drawing device is abutted simultaneously with the restoration of the ejecting capability.
A liquid ejecting apparatus of the present invention includes a liquid ejecting head of the present invention, an ink tank for holding a liquid to be ejected by the liquid ejecting head, and a mounting section on which the liquid ejecting head is mounted.
The liquid ejecting apparatus of the present invention arranged as described above includes the atmosphere communication path for communicating the second liquid flow path, in which the bubble forming liquid exists, to the atmosphere and removes remaining bubbles generated in the second liquid flow path from the atmosphere communication path. That is, the head cartridge is provided only with the communication path for communicating the second liquid flow path with the atmosphere as an arrangement for removing the remaining bubbles, and it is not necessary to provide the liquid ejecting head with a collection path for removing the remaining bubbles, a mechanism for circulating the bubble forming liquid, and the like. Further, in the liquid ejecting head provided with the liquid ejecting apparatus of the present invention, since the atmosphere communication path and the ejecting port are formed through the same surface, when the liquid to be ejected in the ejecting port is drawn by a drawing device having a drawing unit abutted against the ejecting port in order to restore, for example, the ejecting capability of the ejecting port, the remaining bubbles in the atmosphere communication path also can be drawn and removed without changing a direction in which the drawing unit of the drawing device is abutted simultaneously with the restoration of the ejecting capability.
A liquid ejecting apparatus of the present invention may include a drawing device for drawing a liquid to be ejected from the ejecting port of the liquid ejecting head as well as for drawing a bubble forming liquid and remaining bubbles from the atmosphere communication path. Further, the drawing device may draw the liquid to be ejected as well as the bubble forming liquid and the remaining bubbles simultaneously or may draw the liquid to be ejected and the remaining bubbles individually.